Pre-development latensification using polyalkylene amines



United States Patent Otlice 3,256,898 Patented August 16, F366 3,266,898 PIKE-DEVELOPMENT LATENSIFICATIGN USING PDLYALKYLENE AMTNES Marilyn Levy, Red Bank, NJL, assignor to the United itftes of America as represented by the Secretary of the y No Drawing. Filed Oct. 29, 1961, Ser. No. 146,663 6 tClaims. (Cl. 96-65) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This application is a continuation-in-part of the application of Marilyn Levy, Serial Number 758,871, filed September 3, 1958, now abandoned, for Post Latensification of Photographically Sensitive Materials.

This invention relates to a method of increasing the efifective speed of silver halide photographic emulsions.

Several methods of increasing the useful film speed of photographic emulsions have been described in photographic literature and used in practice. Examples of such prior methods are as follows: The use of high speed developers or extended development time; hypersensitization or treatment before camera exposure; intensification after development; and latent image intensification or latensification between exposure and development. Latensification may be accomplished by bathing the emulsion in a solution of certain chemicals, exposure to vapors or exposure to light. This invention relates to latensification by bathing.

Prior methods of latensification by bathing after exposure and before development have included certain procedural techniques which render such methods unsatisfactory. According to these prior procedures, the film must be bathed for prolonged periods and then squeegeed and dried at normal temperature before it can be developed in the conventional manner. The inconvenience of drying film at room temperature in the dark precludes the practical utilization as a method of increasing film speed.

The present invention is based on the discovery that certain chemical compounds, the nature of which will be specified later, serve to effectively increase the film speed of silver halide photographic emulsions when used as a post latensification bath after exposure, and before development. The latent image is intensified by pre-bathing for a minute or less in a very dilute solution of these compounds. Following this treatment, the wet film, which can be washed free of the latensification solution, if desired, is placed directly in any developer and processed in the conventional manner to yield a speed increase of two to four times that'of a film processed in developer only. The necessity for drying film after post-latensification is eliminated. Moreover, there is no increase in gamma over that obtained from normal development.

The bath in which the emulsion is treated prior to development is a dilute aqueous solution of the general class of compounds called polyalkylene amines having the formula- Wherein x and y are integrals not greater than 4 and n ranges from O to 4 and in which R is selected from the group consisting of alkyl radicals and hydrogen.

It is a primary object of the invention to provide a technique for increasing the effective sensitivity of silver halide photographic emulsions.

A further object of the invention is to provide a method for increasing effective sensitivity in silver halide photographic emulsions while at the same time retaining substantially all of the quality characteristics inherent in the film when processed normally Without the benefit of increased speed contributed by the invention.

A further object of the invention is to provide a method of increasing effective sensitivity in silver halide photographic emulsions without appreciably increasing the total processing time.

A further object of the invention is to provide a method of substantially increasing the effective sensitivity of a silver halide photographic emulsion without a change in gamma.

Other objects and features of the invention will more fully appear from the following description and will be particularly pointed out in the claims.

To provide a better understanding of the invention specific examples of suitable materials and techniques for the practice thereof will be described.

Prior to the invention substances which had been used to effect post latensification had not been wholly satisfactory since they involved extra processing steps and produced undesirable effects upon the emulsion which resulted in serious deviation in the characteristics of the processed image from that of a normally processed film without latensification. The invention supplies suitable chemical substances for the practice of latensification and simplifies the procedure.

It has been found that the speed of an emulsion can be doubled or quadrupled by bathing it after exposure and before final processing in an aqueous solution of a compound belonging to the general class of compounds called polyalkylene amines. Examples of compounds in this class are ethylene diamine, propylene diamine, triethylene tetramine, tetraethylene pentamine, and diethylene triamine.

The procedure for treating emulsions is as follows: The emulsion is first exposed in the camera according to the desired speed rating, which would normally be about three times faster than the manufacturers speed rating. After exposure the film is bathed in an aqueous solution of ethylene diamine or other compounds above stated. Although it is not essential, the emulsion may then be washed slightly to remove the ethylene diamine and prevent contamination of the developer. At this time the film may be treated in the same manner as any exposed film. The latensification effect is not changed by the washing or any subsequent processing. It may now be developed to the desired gamma in any standard developer or any specialized developer including the fast acting or slow acting types. It is then fixed in the conventional manner and dried. If the emulsion is developed in a developer for the recommended time, it will have the same gamma as it would have if it had been processed without the post latensification bath.

In the treatment procedure the time periods and the concentration of the post latensification bath are not critical. The concentration of the bath may vary from .05 to .3 molar solution in water. Bathing time may be 15 seconds to 5 minutes. Washing time may vary from 0 to 10 minutes.

3 Any silver halide type emulsion may be processed by the method of the invention. Typical examples of such film are Eastman Panchromatic Negative Tri-X film, Kodak T ri-X Aerecon film and Kodak Plus-X Aerecon film. In the following examples the latter film was used.

Example 1 The exposed film was first bathed for 1 minute in a .2 molar solution of propylene diamine, then washed for 2 minutes and developed in the following formula for 1 minute:

Water liter 1 p-Methylaminophenol sulphate g 3 Sodium sulphite g 45 Hydroquinone g 12 Sodium carbonate g 80 Potassium bromide g 2 The film was then fixed, Washed and dried.

Example 2 The exposed film was first bathed for /2 minute in a .1 molar solution of triethylene tetramine, then washed for 8 minutes and developed in the following formula for 1 minute:

Water liter 1 Sodium sulphite g 91 Sodium carbonate g 165 Potassium bromide g 4 Hydroquinone g 40 1-phenyl-3 pyrazolidone g 1 Benzoltriazole g .4

The film was then fixed, washed and dried.

Example 3 The exposed film was first bathed in a .4 molar solution tetraethylene pentamine for 15 seconds, then washed for 1 minute and developed in the following formula for 4 /2 minutes:

Water liter 1 p-Methylaminophenol sulphate g 2.5 Sodium sulphite g 50 Hydroquinone g 2.5 Sodium metaborate g 20 Potassium bromide g .5

The film was then fixed, washed and dried.

Example 4 The exposed film was first bathed in a .3 molar solution of diethylene triamine for 30 seconds, then washed for 5 minutes and developed in the following formula for minutes:

Water liter 1 p-Methylaminophenol sulphate g 2 Sodium sulphite g 100 Hydroquinone g 5 Borax g 2 Then fix, wash and dry the film.

Example 5 The exposed film was first bathed in a .1 molar solution of ethylene diamine for 1 minute, then washed for 1 minate and processed in the following monobath formula for 2 to 3 minutes:

Water liter 1 Sodium sulphite g 60 Hydroquinone g 30 Sodium hydroxide g 25 1-phenyl-3 pyrazolidone g 3 Sodium thiosulphate g -250 Formaldehyde, 37% cc 10 The film was then rinsed and dried.

In the above examples of the practice of the invention the Kodak Plus-X Aerecon film used showed an increased speed of from 2 to 4 times its rated speed of A.S.A. 80. The other film types processed showed a similar increase in speed.

What is claimed is:

1. A method of processing silver halide photographic emulsions to increase their effective speed comprising exposing the emulsion, then first bathing the emulsion for from 15 seconds to 5 minutes in an aqueous solution of a compound having the structural formula in which x and y are integrals not greater than 4 and n ranges from 0 to 4 and in which R is selected from the group consisting of alkyl radicals and hydrogen said solu tion having a concentration of from .05 to .5 molar in water and thereafter developing and fixing the image in solution separate from the said first bath.

2. A method of processing silver halide photographic emulsions according to claim 1 and wherein the said first bath is an aqueous solution of ethylene diamine having a concentration of .05 to .5 molar in Water.

3. A method of processing silver halide photographic emulsions according to claim 1 and wherein the said first bath is in an aqueous solution of propylenediamine having a concentration of .05 to .5 molar in water.

4. A method of processing silver halide photographic emulsions according to claim 1 and wherein the said first bath is an aqueous solution of diethylene triamine having a concentration of .05 to .5 molar in water.

5. A method of processing silver halide photographic emulsions according to claim 1 and wherein the said first bath is an aqueous solution of tetraethylene pentamine having a concentration of .05 to .5 molar in Water.

6. A method of processing silver halide photographic emulsions according to claim 1 and wherein the said first bath is an aqueous solution of triethylene tetramine having a concentration of .05 to .5 molar in water.

References Cited by the Examiner UNITED STATES PATENTS 2,201,591 5/1940 Moreno 9665 2,518,698 8/1950 Lowe et al. 96107 2,743,182 4/1956 Lowe et a1. 96-107 2,857,275 10/1958 Land et a1 9629 3,017,271 1/1962 Piper 96107 OTHER REFERENCES Glafkides, Photographic Chemistry, vol. 1, Fountain Press, London, 1958, pp. 3436 relied on.

NORMAN G. TORCHIN, Primary Examiner.

LOUISE P. QUAST, Examiner. A. L. LIBERMAN, C. DAVIS, Assistant Examiners, 

1. A METHOD OF PROCESSING SILVER HALIDE PHOTOGRAPHIC EMULSIONS TO INCREASE THEIR EFFECTIVE SPEED COMPRISING EXPOSING THE EMULSION, THEN FIRST BATHING THE EMULSION FOR FROM 15 SECONDS TO 5 MINUTES IN AN AQUEOUS SOLUTION OF A COMPOUND HAVING THE STRUCTURAL FORMULA H2N- (CHR)X-(CHR)Y-NH!N -(CHR)X-(CHR)Y-NH2 IN WHICH X AND Y ARE INTEGRALS NOT GREATER THAN 4 AND N RANGES FROM 0 TO 4 AND IN WHICH R IS SELECTED FROM THE GROUP CONSISTING OF ALKYL RADICALS AND HYDROGEN SAID SOLUTION HAVING A CONCENTRATION OF FROM .05 TO .5 MOLAR IN WATER AND THEREAFTER DEVELOPING AND FIXING THE IMAGE IN SOLUTION SEPARATE FROM THE SAID FIRST BATH. 